docs(api): align catalog contract with the AgentEndpoint implementation

[TOMOKI977]

Closes #98

Summary

Aligns the catalog part of the API contract (#77) with the AgentEndpoint implementation in #88, so #88 and #90 can merge as they are for the Stellar Elite demo.

• AgentEndpoint.list() / get(id: String) replace CatalogEndpoint.listAgents() / getAgent(agentId: int).
• New Agent catalog section: the two identifiers (metadata id for get, on-chain registryId for createHire and the escrow), ordering, outage behaviour, and the typed AgentCatalogUnavailable exception.
• AgentSummary and AgentCatalogUnavailable models copied byte for byte from feat(server): add agent catalog endpoint backed by registry metadata #88.
• Fields the MVP doesn't serve yet (rating, paidHireCount, active, owner, structured skills, explorerUrl, chainDataFresh, input limit) are listed as planned, each with its target issue.
• HireDetail.agent and the F2, F3, F5 and F7 traceability rows use the new names.

Acceptance criteria

• Endpoint and model names in api.md match puls3_server on the feat(server): add agent catalog endpoint backed by registry metadata #88 branch exactly
• Fields the MVP does not serve yet are marked as planned
• Agent identifiers used by hire endpoints are consistent with the catalog's identifiers (agentId = AgentSummary.registryId)

Verification evidence

• agent_summary.spy.yaml and agent_catalog_unavailable.spy.yaml compared with diff against puls3_server/lib/src/agent/ on feat(server): add agent catalog endpoint backed by registry metadata #88: identical.
• Endpoint rows checked against agent_endpoint.dart on feat(server): add agent catalog endpoint backed by registry metadata #88 (public, no requireLogin, registered as agent).

Notes for reviewers

• The catalog is documented as the one exception to contract rule 7 (typed exception instead of Puls3ApiException). Moving it to the shared error catalog can be a follow-up.
• Please confirm the target issues in the planned-fields table, especially active → feat: register agent flow (wallet and on-chain identity) #18.
• DeployResult.agent still points to the planned Agent model; it belongs to Agent Studio (feat: Agent Studio endpoints (drafts, test run, deploy) #35).

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[moises-cisneros]

Approving. I compared the doc against the server code and the models: agent_summary.spy.yaml and agent_catalog_unavailable.spy.yaml in docs/architecture/models/ are identical to the server ones (comments aside), and the endpoint methods, 60s TTL, nullability of wallet? / model? and the dedup by highest registryId match AgentEndpoint / agent_catalog_service. The branch merges cleanly with current main.

Non-blocking:

• api.md:239 and the comment in puls3_api_exception.spy.yaml:10-11 still list CatalogUnavailable, ChainDataUnavailable and AgentNotFound as catalog codes. api.md:245 explains it, but the spy comment has no such note.
• HireDetail.agent is resolved by registryId == hire.agentId, and the catalog drops superseded duplicates. The doc does not say what HireDetail.agent is for a hire on a superseded registry id.
• The docs copy the server .spy.yaml files "exactly", but nothing enforces it, so they can drift.

[TOMOKI977]

Merged into main as 34a8032 (squash), which closes #98. Thanks @moises-cisneros for checking the doc against the server models.

Your three non-blocking notes (the catalog codes in the puls3_api_exception.spy.yaml comment, HireDetail.agent for a superseded registry id, and drift between the docs and server .spy.yaml copies) are still open; I'll pick them up in a follow-up.